1. Field of the Invention
This invention relates to an ink ejecting device in which the surface of a nozzle portion is coated with a water-repellent film and the nozzle surface is further treated to prevent the nozzle surface from becoming electrically charged.
2. Description of the Related Art
Generally, in an ink ejecting device which ejects ink to form an image, a water-repellent film is formed on the nozzle surface to prevent the nozzle from being clogged with, for example, drops of ink adhering to the circumference of the ink-ejecting nozzle. Further, an antistatic treatment is applied to the nozzle surface so that dust and the like will not attach to the nozzle surface.
Known antistatic treatments include a method in which, as described in Japanese Patent Laid-open Nos. 61-291148 and 61-291149, a metallic conductive filler is mixed into the nozzle substrate resin which is used to form the nozzle plate. This nozzle plate is used in an ink ejecting device having a water-repellent film formed on the nozzle surface. Alternately, the metallic conductive filler is mixed in the water-repellent film, and the nozzle substrate resin or the water-repellent film is grounded. Other known methods include a method in which a surface active agent is applied to the water-repellent film and a method in which a metallic thin film is formed on the water-repellent film.
With the recent increase in the packaging density in ink ejecting devices, nozzles having a diameter of 20 .mu.m-50 .mu.m are formed in a nozzle plate at a small pitch (or center-to-center interval) by excimer laser beam drilling. In such processing, if the water-repellent film is formed after the nozzles have been formed, the nozzles become clogged with the water-repellent film. Therefore, the nozzles must be formed after the water-repellent film has been formed.
However, in the above-described known methods for applying the antistatic treatments to the ink ejecting devices, when a metallic conductive filler is mixed into the nozzle substrate resin or the water-repellent film, the metallic conductive filler cannot be processed by the excimer laser beam. Thus, it becomes impossible to drill fine nozzles, Also, in the method in which a metallic film is formed on a water-repellent film, it becomes much more difficult to form the nozzles with the excimer laser beam.
On the other hand, if the metallic thin film is formed on, or a surface active agent is applied to, the nozzle surface so that the thin metallic film or surface active agent layer does not affect the excimer laser beam processing, the thin film or the applied surface active agent layer wears away from or peels off of the nozzle surface due to wiping operations to remove ink, dust or the like from the nozzle surface. Thus, this method has a problem that the useful lifetime of the antistatic treatment is too short.